Aoyama, a child with adult-like knowledge, faces teasing from classmates but harbors a crush on a woman he met at the dentist. When penguins inexplicably appear in his town, Aoyama, alongside his crush, delves into unraveling this enigma. Their exploration leads them to 'The Sea,' a hovering sphere with a peculiar trait - objects entering it vanish without a trace, except those destroyed by the penguins. As they delve deeper, a chilling discovery unfolds. 'Penguin Highway' tracks Aoyama and the woman's quest to unveil the penguins' origins and the challenges Aoyama encounters in his investigative journey.